The case reported here fulfilled the Centers for Disease Control surveillance case definition for acquired immunodeficiency syndrome without laboratory evidence of human immunodeficiency virus. The patient, a 63-year-old man, had received transfusions of several units of packed red blood cells after a coronary bypass graft. He had recurrent fever and lymphopenia. He had a depressed helper T-cell count, esophageal and tracheobronchial candidiasis, and Pneumocystis carinii pneumonia. Results of all tests for human immunodeficiency virus were negative or inconclusive. However, the patient may have been seroconverting at the time of his death.